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Review of Scientific Instruments

Issue 1 • Date Jan 1978

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Displaying Results 1 - 25 of 33
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Microparticle accelerator of unique design

    Page(s): 1 - 7
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    A microparticle accelator of unique design, which produces high‐velocity, micrometer‐sized projectiles of any cohesive material, is described. In the source, an electrodynamic levitator, single particles are charged by ion bombardment in high vacuum. The vertical accelerator has four drift tubes, each initially at a high negative voltage. After injection of the projectile, each tube is grounded in turn at a time determined by the voltage and charge/mass ratio to give four acceleration stages with a total voltage equivalent to about 1.7 MV. The delay times may be set manually or controlled automatically by the particle’s charge/mass ratio measured in the source by the operator just before ejection. At the entrance to the accelerator, the particle generates a signal that initiates the timing sequence. In the target chamber, detectors record the passage of the particle and provide information on charge, velocity, and position. Trajectories usually pass within a 1‐mm‐radius circle 1 m below the fourth drift tube. Velocities between 0.5 and 15 km/s have been attained with projectiles of various materials and shapes for cratering studies and calibration of micrometeoroid detectors. About 20 projectiles per day can be accelerated. View full abstract»

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  • Interpretation of electrostatic energy analyzer data of a flowing plamsa

    Page(s): 8 - 10
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    Extracting correct plasma parameters from the experimental data from a retarding field electrostatic energy analyzer in a flowing plasma requires proper interpretation of the effect of plasma flow on the collector current. In this paper, relationships for computing plasma parameters directly from the analyzer data are described for any type of velocity distribution of particles. View full abstract»

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  • Study of the piston‐rotation technique for piston‐cylinder devices

    Page(s): 11 - 14
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    In piston‐cylinder studies of reconstructive phase transitions, piston rotation plays a more subtle role than has previously been thought. Rotation of the piston not only relieves sliding friction, but also helps to activate sluggish transformations. This suggests modification of the traditionally accepted volumetric technique, and of the standard interpretation of data. View full abstract»

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  • Micro‐Fresnel zone plates for coded imaging applications

    Page(s): 15 - 20
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    Design considerations and fabrication procedures for Fresnel zone plates appropriate for high‐resolution coded imaging of x‐ray and particle emission from laser produced plasmas are presented. Fabrication results for free standing zone plate structures of high Z material (gold), large zone number (100⩽n⩽240), microscopic minimum linewidth (2.6⩽Δr⩽10.2 μm), and appreciable material thickness (1⩽t⩽7 μm) are reported. View full abstract»

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  • Optimization and performance of electrostatic particle analyzers

    Page(s): 21 - 23
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    Experiment and simple theory provide a description of the performance of planar gridded electrostatic particle analyzers in magnetoplasma. View full abstract»

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  • Automated apparatus for evaporation and in situ measurements of multiple thin films

    Page(s): 24 - 30
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    We describe a system for vacuum deposition which measures as well as controls substrate temperature, film thickness, and rate of evaporation. By measuring the resonant frequency of a quartz crystal oscillator which has been calibrated for thickness, we produce films of 11 different thicknesses in a single evaporation. The system is then capable of immediately initiating four‐probe resistivity measurements on the evaporated films every 90 s, allowing the measurement of rapid structural changes. The system is calculator‐based and interfacing is achieved with plug‐in compatible instrumentation using the IEEE standard 488‐1975 interface bus. View full abstract»

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  • Full‐photon‐counting Rayleigh spectrometer: a correlation and/or fast Fourier transform instrument

    Page(s): 31 - 38
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    A fast, flexible, and relatively inexpensive minicomputer based Rayleigh spectrometer has been constructed. This spectrometer can utilize photon pulses in a most efficient way by performing autocorrelation and/or FFT with any desired number of channels. Its capability has been demonstrated by measuring large latex particles, small sodium dodecyl sulfate micelles, and a polydisperse latex‐γ‐globulin system. Detailed timing diagrams and circuit schematics are also included. View full abstract»

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  • Picosecond‐resolution fluorescence lifetime measuring system with a cw laser and a radio

    Page(s): 39 - 44
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    A procedure for measurement of fluorescence lifetimes with picosecond time resolution is described. A cw laser beam is modulated with a standing‐wave acousto‐optic modulator. The modulated beam is split; one part serves as a reference beam, the other part excites the fluorescent sample. The sample flourescence and the reference beam, attenuated and delayed optically to be equal in amplitude and opposite in phase to the fluorescence, are incident onto a single photomultiplier tube. The thus achieved photodetector ac null is monitored either by an AM radio, whose intermediate‐frequency signal is displayed on an oscilloscope, or by a spectrum analyzer. With 30‐MHz light modulation and the radio, lifetimes could be determined with resolution better than 15 ps. With the spectrum anlyzer and 170‐MHz light modulation frequency we have achieved 4‐ps lifetime resolution. Correction for photomultiplier transit time versus incident wavelength is made. View full abstract»

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  • Sensitivity considerations for NMR in metal single crystals

    Page(s): 45 - 49
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    We report a study of the factors determining the sensitivity of NMR measurements using bulk metal single crystal samples. We show that, in an ideal case, the NMR signal intensity from such a sample can be characterized by a figure of merit which is a function of only the fractional radio‐frequency power losses in the coil winding compared to the losses in the sample. This allows the Q factor of the NMR coil to be varied considerably with no appreciable change in the figure of merit, thus permitting the coil Q to be chosen on the basis of the noise characteristics of the spectrometer being used. Measurements indicate that the absolute signal intensity from a metal single crystal with a near‐optimum coil is about 1/10 of that from a powdered sample with particle radii approximately equal to the rf skin depth. View full abstract»

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  • Pressure vessel for tensile testing in high‐pressure gases at elevated temperatures

    Page(s): 50 - 51
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    A pressure vessel for tensile testing has been developed to measure tensile stress in high‐pressure up to 50.5 MPa at elevated temperatures up to 773 K. The vessel is designed to facilitate the measurement of the actual tensile load on the specimen by an external load cell without the influence of axial stress due to high pressure in the vessel and the effect of friction at sliding seals where the load rod enters the vessel. Application of the vessel to tensile testing of a steel in hydrogen atmosphere is briefly described. View full abstract»

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  • Low‐noise amplification of voltage and current fluctuations arising in epithelia

    Page(s): 52 - 57
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    Two low‐noise differential input amplifiers designed for voltage and current fluctuation measurements in epithelia are described. The first one uses a matched pair of low‐noise transistors and is particularly suited for low‐frequency current and voltage noise measurements in frog skin and other preparations with impedances below 1 kΩ. The second one is designed around a matched pair of JFETs and can also be used for higher source impedance. Performance is demonstrated with Na+ current power density spectra obtained from frog skin with the transistor‐input stage. View full abstract»

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  • Polycrystalline techniques for conductivity studies of organic charge transfer salts

    Page(s): 58 - 62
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    Polycrystalline compaction conductivity measurements are extensively used to characterize newly synthesized quasi‐one‐dimensional organic charge transfer salts. This technique, however, can be both quantitatively and qualitatively misleading. Studies of the polycrystalline compaction and single crystal conductivities of a variety of tetracyanoquinodimethan (TCNQ) salts allow us to define the limits of reliability of the polycrystalline compaction technique, and denote its shortcomings. A new polycrystalline technique, the voltage shorted compaction (VSC), is described. The VSC has proven to be a valuable aid in characterizing the electrical properties of new materials where single crystals are difficult to produce. View full abstract»

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  • Fast and simple photometric signal processing unit

    Page(s): 63 - 64
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    A simple and fast photometric signal processing unit has been constructed using some of the commonly available linear and digital integrated circuits. A common mode rejection ratio of 75 dB, based on the subtraction of the output and reference signal, and a rise time of 0.2 μs have been achieved with this instrument. View full abstract»

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  • Single line CCD camera to improve positioning

    Page(s): 65 - 67
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    This article describes an opto‐electronic device that allows on‐line visualization of the optical intensity function along a strip. The use of a linear optical charge‐coupled device (CCD) array eliminates all moving parts. This makes adaptation to a standard microscope possible without modifications. The setup described here is essential where precise positioning of a reference graticule on diffuse lines must be performed. View full abstract»

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  • Stability of germanium resistance thermometers at 20 K

    Page(s): 68 - 73
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    Thirty germanium resistance thermometers have been thermally cycled 100 times between 20 and 300 K, and their stability at 20 K has been evaluated. The results reveal a wide range of stabilities, ranging from 0.1 to 20 mK. Five different modes of behavior have been provisionally classified as stable, drifting, jumping, bimodal, and irregular. View full abstract»

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  • Variable temperature UHV dual‐range cell for spectroscopic surface studies

    Page(s): 74 - 76
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    A stainless steel cell for transmission spectroscopy of surface compounds is described. This cell allows subsequent spectra recording of the sample in two spectral regions requiring different window materials. The sample temperature can be varied from 100 to 700 K, the pressure from 10-6 to 105 Pa. The mean temperatue is measured inside the wafer with a thin platinum wire as a resistance thermometer. View full abstract»

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  • Conical slow wave antenna as a plasma source

    Page(s): 77 - 79
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    A simple conical helix has been successfully employed as a slow wave structure to generate plasmas by electron cyclotron resonance heating (ECRH). The plasma is typical of plasmas created by ‘‘Lisitano coil’’ sources, n∼1010–1012 cm-3 with Te≈2–20 eV. This source, however, is much simpler to fabricate. The ease of fabrication allows the user some flexibility in designing the source to fit a specific plasma physics experiment. View full abstract»

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  • Uniformity condition for a rectangular field coil with a split winding

    Page(s): 80 - 82
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    A generalized Helmholtz condition for field uniformity is derived from the closed form solution of the magnetic field in a multilayer rectangular coil pair as a function of coil dimensions and pair separation. The relation among the dimensions satisfying this condition is found and plotted in parametric form for single layer coils and for a multilayer coil with a specific winding thickness. For square coils of cross section small compared to their mean radius, the gap separation approaches half the coil radius, analogous to the classical condition for circular coils. Comparison between theoretical and measured values for tolerances within ±5% of the field at the system center agree within a 6% maximum deviation. For the experimental coil, the area enclosed by the ±5% contour was 58% of the area of the full coil. View full abstract»

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  • Precision grinding device for radioactive tracer diffusion studies in very hard ceramic materials

    Page(s): 83 - 85
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    Precision grinding equipment for the removal of very thin layers of hard materials containing slowly diffusing isotope tracers is described. The system is unique in the use of vacuum techniques to hold the sample in place and in the procedures used to insure maintenance of an optically flat sample with essentially parallel faces throughout the removal process. View full abstract»

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  • Portable 3He detector cryostat for the far infrared

    Page(s): 86 - 88
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    A portable 3He cryostat for far infrared detection applications is described. The cryostat has been used for a number of years in aircraft‐ , observatory‐ , and laboratory‐based research. Some related studies of various bolometric materials are also reported. View full abstract»

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  • Optical technique for the study of convective diffusion from falling drops

    Page(s): 89 - 93
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    A recently developed deflection mapping technique has been exploited for measurement of rate of mass transfer from a liquid drop falling freely in another liquid medium. Results have been found to be in good agreement with theory. Simultaneously, measurement of the diffusion coefficient is also reported. View full abstract»

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  • Appartus for high‐resolution surface tension measurement

    Page(s): 94 - 100
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    We describe an apparatus for measuring surface tension of insulating liquids by capacitive sensing of capillary rise. Two guarded coaxial capacitors with different gap widths are connected to permit liquid to flow between them. The higher capillary rise in the narrow‐gap capacitor is balanced by a dc voltage applied to the wide capacitor by a servosystem. In a measurements of the surface tension of liquid helium we obtain a resolution of 1 part in 105. The technique is well suited for automated measurements of small changes in surface tension. View full abstract»

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  • Air‐lock system for the transfer of reactive samples to the Philips EM 300S electron microscope

    Page(s): 101 - 103
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    An air‐look system has been developed in order to transfer reactive samples under vacuum from any preparation facility to the high‐resolution stage of the Philips EM 300S electron microscope. The system has been tested using the highly hygroscopic material strontium chloride prepared in the form of small particles. Based on the shape of the particles and the associated diffraction pattern, it has been shown that the air‐lock transfer system effectively prevents hydration in the case of small SrCl2 particles. View full abstract»

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  • Laser‐driven 3 kA x‐ray source

    Page(s): 104 - 110
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    An x‐ray source driven by a 10‐pps Nd–YAG laser is described which, because of its high peak power and automatic synchronization to the laser, is especially suited for the study of x‐ray optical interactions. The device is of very simple construction, is based upon a 1‐m‐long 3‐Ω coaxial transmission line charged to 40 kV, and delivers 20‐ns wide pulses at peak currents of ∼3 kA. A simple analysis which is in good agreement with experiment predicts that a 1‐Ω line charged to 60 kV should yield peak currents of ∼15 kA. View full abstract»

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Aims & Scope

Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques.

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Editor
Albert T. Macrander
Argonne National Laboratory